Biology

Cellular Respiration and Enzymes

1,551 Questions

Explore key concepts of cellular respiration, including glycolysis, the Krebs cycle, and the electron transport chain. These questions also cover ATP production, anaerobic respiration, and essential metabolic pathways. This topic forms a core part of the biology syllabus for many competitive examinations.

Glycolysis and metabolic pathwaysKrebs cycle processesElectron transport chainATP production countAnaerobic respiration products

Cellular Respiration and Enzymes Questions

Multiple choice

Energy is stored in the cells as

  1. ATP

  2. DNA

  3. NADP

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

ATP (Adenosine Triphosphate) is the primary energy storage molecule in cells. DNA stores genetic information, NADP is involved in photosynthesis, and ATP is the universal energy currency.

Multiple choice

Various inhibitors are used in the study of the electron transport system at various levels of electron carriers.

Which of the following substances acts as an inhibitor of the electron transport system between the flavoproteins and coenzyme Q?

  1. Atractyloside

  2. Bactoprenol

  3. Amytal

  4. Azurin

  5. Antimycin A
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Amytal (5-ethyl-5-isoamylbarbituric acid) is a barbiturate drug that inhibits the electron transport system between the flavoproteins and coenzyme Q.

Multiple choice

When one molecule of FADH2 is oxidised to FAD, the number of ATP produced is

  1. one

  2. two

  3. three

  4. four

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In the electron transport chain, each FADH2 molecule yields approximately 1.5 to 2 ATP molecules (modern estimates use 1.5, older textbooks used 2). FADH2 enters the chain at Complex II (coenzyme Q), bypassing Complex I, so it pumps fewer protons and generates less ATP than NADH, which yields 2.5 to 3 ATP.

Multiple choice

What is the energy currency of a cell?

  1. GTP

  2. ATP

  3. ADP

  4. NADP
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Energy is usually liberated from the ATP molecule to do work in the cell by a reaction that removes one of the phosphate-oxygen groups, leaving adenosine diphosphate (ADP).

Multiple choice

Which of the following assumptions is/are made to make calculations of the net gain of ATP for every glucose molecule oxidised?

  1. Only glucose is being respired

  2. No other intermediate in the pathway is utilised to synthesise any other compound.

  3. The NADH synthesised in glycolysis is transferred into the mitochondria.

  4. A sequential orderly pathway is functioning.

  5. All of the above
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This is the correct option as all of the above are assumptions to make calculations of the net gain of ATP for every glucose molecule oxidised.

Multiple choice

Which of the following statements is/are false?

a. In anaerobic organisms, glycosis is the only process in respiration. b. Glucose undergoes partial oxidation in glycosis to form two molecules of pyruvic acid. c. Sucrose is converted into glucose and fructose by the enzyme hexokinase.

  1. Only a

  2. Only a and b

  3. Only b

  4. Only b and c

  5. Only c
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This is the correct option as this statement is false. Sucrose is converted into glucose and fructose by the enzyme invertase.

Multiple choice

Which of the following statements is/are false?

a. In eukaryotes, aerobic respiration takes place within the cytoplasm. b. In many prokaryotes, fermentation takes place under anaerobic conditions. c. The metabolic pathway through which the electron passes from one carrier to another is called the electron transport system.

  1. Only a

  2. Only a and b

  3. Only b

  4. Only b and c

  5. Only c
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is the correct option as this statement is false. In eukaryotes, aerobic respiration takes place within the mitochondria.

Multiple choice

Which of the following is not a characteristic property of aerobic respiration?

  1. In aerobic respiration, there is a complete oxidation of pyruvate.

  2. In aerobic respiration, two molecules of NADH are produced from the metabolism of two molecules of pyruvic acid.

  3. NADH is oxidised to NAD+ very slowly in aerobic respiration.

  4. Glucose is completely degraded to CO2 and H2O in aerobic respiration.

  5. In aerobic respiration, many molecules of ATP are generated.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This is the correct option as this is not a characteristic property of aerobic respiration.